question

Comparing the mass of 1 molecule and 1 mol of H2O. Both masses have the same number but different units (atomic mass units and grams). Expressing both masses in grams indicates their huge difference: 1 molecule H2O has a mass of 2.99×10−23 g whereas 1 mol H2O has a mass of 18.0 g. How many H2O molecules are in a 9.00-g sample of water?

answer

Use Avogadro's number of molecules (6.02X10^23). 1 molecule of H2) is 18 amu and 1 mol is 18g. So since it is half the number of grams for 1 mol, just simply divide Avogadro's number by 2 and the answer is 3.01*10^23

question

What number would you use to convert moles of CH4 to grams of CH4?

answer

The molar mass, 16.0 g/mol.

question

What number would you use to convert number of molecules of CH4 to moles of CH4?

answer

Avogadro's number, 6.02×1023/1 mol.

question

How do you calculate the mole ratio of each element in any compound?

answer

By dividing the molecular weight of the element by the empirical formula weight.

question

Write a balanced chemical equation for the reaction that occurs when Mg(s) reacts with Cl2(g).

answer

Mg(s)+Cl2(g)→MgCl2(s)

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question

Write a balanced chemical equation for the reaction that occurs when barium carbonate decomposes into barium oxide and carbon dioxide gas when heated.

answer

BaCO3(s)→BaO(s)+CO2(g)

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question

Write a balanced chemical equation for the reaction that occurs when the hydrocarbon styrene, C8H8(l), is combusted in air.

answer

C8H8(l)+10O2(g)→8CO2(g)+4H2O(l)

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Chm 151 – Chemistry – Flashcards

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